Just like, should the toilet paper go over or under, there are two camps: drysuit divers who use their BCDs for buoyancy and those who use their drysuits. No right way - just endless discussion. I'm in the drysuit for buoyancy camp and leave my valve open during the dive. My BCD is for emergency backup and surface flotation.

Yes, while taking pictures, I sometimes have air bleed out the valve, but this isn't a major problem - just add some more air to the suit or change positions. (I dive a DUI TLS-350).